Bug 570058 made it so file fragmentation is minimized for partial updates. To do this for complete updates we should store each file size for added files. Since added files are not all that fragmented it might not be worth fixing this bug especially since any partial update to the file will defragment it but the cost / reward tradeoff should be evaluated.

Sample of fragmentation when performing a complete update on Win7 xul.dll 8 omni.jar 4 mozjs.dll 3 libGLESv2.dll 2 mozalloc.dll 2 mozcpp19.dll 2 mozcrt19.dll 2 mozsqlite3.dll 2 nss3.dll 2 plc4.dll 2 plugin-container.exe 2 So far in my testing, each file that is fragmented that is patched by a future partial will be made contiguous if there is contiguous space available due to Bug 570058. I think it would be a good thing to fix this bug but it is not where as important to fix as Bug 570058 was.